Upgrade to Pro — share decks privately, control downloads, hide ads and more …

Writing Beautiful Code - EuroPython 2017

Writing Beautiful Code - EuroPython 2017

Slides of my talk "Writing Beautiful Code" at Euro Python 2017.

Anand Chitipothu

July 11, 2017
Tweet

More Decks by Anand Chitipothu

Other Decks in Programming

Transcript

  1. Programs must be written for people to read, and only

    incidentally for machines to execute. - Structure and Interpretation of Computer Programs (The Wizard Book)
  2. Nouns & Verbs Use nouns for variables and classes. size,

    price, Task, Scheduler, Bank Account Use verbs for functions. get_file_size, make_account, deposit
  3. largest_line(lines) files = os.listdir(directory) file = os.listdir(directory) for lines in

    open(filename).readlines(): sum += int(lines) Use plural for a list
  4. Reserve Loop Indexes Use i, j only as loop indexes.

    for i in range(10): print i for i in numbers: result += i for n in numbers: result += n
  5. Can you improve this? def get_data(x, y): z = []

    for i in x: z.append(i[y]) return z Example 1
  6. def get_column(dataset, col_index): column = [] for row in dataset:

    column.append(row[col_index]) return column Example 1
  7. Never use similar names for completely different datatypes. a1 =

    [1, 2, 3] a2 = len(x) values = [1, 2, 3] n = len(x) Similar names
  8. Don’t say the obvious # increments x by 2 x

    = x + 2 # compensate for border on both the sides x = x + 2
  9. # The following is an optimization to saves # lot

    of memcache calls. Handle with care! ... Explain why you made that choice
  10. # -- XXX -- Anand - Sep 2015 -- #

    UTF-conversion was failing for a chinese # user for reasons I couldn't understand. # Added "ignore" as second argument to handle # that temporarily. name = name.encode("utf-8", "ignore") Document special cases
  11. # find length of the longest line n = max([len(line)

    for line in lines]) n = len(longest(lines)) Make Comments Redundant
  12. Make Comments Redundant # process documents … # upload them

    to search engine … docs = process_documents(...) search_engine_submit(docs)
  13. The 7 ± 2 Rule The number of objects an

    average human can hold in working memory is 7 ± 2. - Miller's Law
  14. def add(input_data): try: x = int(input_data['x']) except ValueError: raise Exception("Invalid

    int value for x") try: y = int(input_data['x']) except ValueError: raise Exception("Invalid int value for y") return x+y Avoid Duplication
  15. def get_int(dictionary, key): try: return int(dictionary[key]) except ValueError: raise Exception("Invalid

    int value for {}".format(key)) def add(input_data): x = get_int(input_data, "x") y = get_int(input_data, "y") return x+y Avoid Duplication - generalize instead
  16. Avoid too many nested levels def update_post(...): post = get_post(..)

    if action == 'update-title': if title == '': ... else: ... elif action == "add-tag": ...
  17. def update_post(...): post = get_post(..) if action == "update-title": update_post_title(...)

    elif action == "add-tag": update_post_add_tag(...) Avoid too many nested levels
  18. Handle errors separately def get_user(email): if valid_user(email): if is_user_blocked(email): return

    Exception("Account is blocked") else: query = "...." row = db.select(query).first() return User(row) else: raise Exception("Invalid email")
  19. Handle errors separately def get_user(email): if not valid_user(email): raise ValueError("Invalid

    email") if is_email_blocked(email): raise Exception("Account blocked") query = "...." row = db.select(query).first() return User(row)
  20. Suppress the implementation details def main(): filename = sys.argv[1] words

    = read_words(filename) freq = wordfreq(words) print_freq(freq)
  21. Summary • Choose meaningful variable names • Use comments when

    required • Split the program into small independent modules & functions • Avoid duplication • Suppress implementation details • Always optimize for readability
  22. - The Tao of Programming “A program should be light

    and agile, its subroutines connected like a string of pearls. The spirit and intent of the program should be retained throughout. There should be neither too little nor too much, neither needless loops nor useless variables, neither lack of structure nor overwhelming rigidity.”
  23. - The Tao of Programming “A program should be light

    and agile, its subroutines connected like a string of pearls. The spirit and intent of the program should be retained throughout. There should be neither too little nor too much, neither needless loops nor useless variables, neither lack of structure nor overwhelming rigidity.”
  24. “A program should be light and agile, its subroutines connected

    like a string of pearls. The spirit and intent of the program should be retained throughout. There should be neither too little nor too much, neither needless loops nor useless variables, neither lack of structure nor overwhelming rigidity.” - The Tao of Programming